Fix some minor inconsistencies in the Package examples

* doc/lispref/package.texi (Simple Packages): Use one of the
approved keywords (bug#19490).

* doc/lispref/tips.texi (Library Headers): Use URL instead of
Homepage to make things consistent with "Simple Packages".

doc/lispref/package.texi

@@ -158,7 +158,7 @@ the various headers, as illustrated by the following example:
 ;; Author: J. R. Hacker <jrh@@example.com>
 ;; Version: 1.3
 ;; Package-Requires: ((flange "1.0"))
-;; Keywords: multimedia, frobnicate
+;; Keywords: multimedia, hypermedia
 ;; URL: http://example.com/jrhacker/superfrobnicate
 
 @dots{}

doc/lispref/tips.texi

@@ -958,7 +958,7 @@ explains these conventions, starting with an example:
 ;; Created: 14 Jul 2010
 @group
 ;; Keywords: languages
-;; Homepage: http://example.com/foo
+;; URL: http://example.com/foo
 
 ;; This file is not part of GNU Emacs.